1. Field
Aspects of the present disclosure relate generally to wireless communication systems, and more particularly, to improving congestion in communication links between NodeBs and radio network controllers.
2. Background
Wireless communication networks are widely deployed to provide various communication services such as telephony, video, data, messaging, broadcasts, and so on. Such networks, which are usually multiple access networks, support communications for multiple users by sharing the available network resources. One example of such a network is the UMTS Terrestrial Radio Access Network (UTRAN). The UTRAN is the radio access network (RAN) defined as a part of the Universal Mobile Telecommunications System (UMTS), a third generation (3G) mobile phone technology supported by the 3rd Generation Partnership Project (3GPP). The UMTS, which is the successor to Global System for Mobile Communications (GSM) technologies, currently supports various air interface standards, such as Wideband-Code Division Multiple Access (W-CDMA), Time Division-Code Division Multiple Access (TD-CDMA), and Time Division-Synchronous Code Division Multiple Access (TD-SCDMA). The UMTS also supports enhanced 3G data communications protocols, such as High Speed Packet Access (HSPA), which provides higher data transfer speeds and capacity to associated UMTS networks.
A further wireless communication protocol based on UMTS is High Speed Downlink Packet Access (HSDPA). In some HSDPA communication networks, a user equipment (UE) is served by two different cells or NodeBs. Such a system may be referred to as a multiflow, Dual-Cell HSDPA or Dual-Carrier HSDPA, or DC-HSDPA system. DC-HSDPA provides joint scheduling across two HSDPA carriers to increase the peak data rates per user and better utilize the available resources. An extension of DC-HSDPA is Single-Frequency Dual-Cell HSDPA (SF-DC), where SF-DC replaces the two carriers in DC-HSDPA by two cells in the same carrier. In a system with SF-DC, if a UE is in softer or soft handover, it will be served by both the primary serving cell (which has the strongest pilot Ec/Io), and the secondary serving cell (which has the second strongest pilot Ec/Io).
In HSDPA, the control of radio frame scheduling, e.g. flow control, is moved from a radio network controller (RNC) to the NodeBs. Typical flow control algorithms assume that the backhaul link, referred to as the Iub link, has unlimited capacity—however, this is not always the case. When the Iub link does not have unlimited capacity, then congestion occurs and the Iub link becomes a bottleneck in the flow control process. Such bottlenecking leads to poor network downlink performance and a corresponding degraded user experience.
As the demand for mobile broadband access continues to increase, research and development continue to advance the UMTS technologies not only to meet the growing demand for mobile broadband access, but to advance and enhance the user experience with mobile communications. Thus, an improved method and apparatus for limiting Iub link congestion in a multiflow environment is needed.